Air compressor



June 2,` 1931. L. H. HYATT 1,808,554

AIR COMPRESSOR Filed Aug. 23, 1927 2 Sheets-Sheet l .lime 2, 1931. y L H, HYATT 1,808,554

AIR COMPRES Sv/OR Filed Aug. 25, 1927 n 2 Sheets-Sheet 2 Y "OQ Z4 ATTORNEYS Patented June 2, 1931 UNITED STATES LAWRENCE H. HYATT, or NEW YORK, N. Y.

AIR cor/rPREsson This invention relates to compressing air .and has for its principal object the provision of an improved compressor constructed so as to operate with a minimum generation of "5 heat in the compression cylinder. c

In the accompanying drawings, I have illustrated a preferred embodiment of my in- Y l:15. cylinder showing the position of the parts duringv successive stages of the compression cycle.

n YThe compressor illustrated in Jthe drawings is of the doublefacting type consisting in VM'220 effect of two compression cylinders in which the actions during each stroke are complementary. As the actions in each cylinder are identical except for this complementary time relation, I shall ingeneral confine the following description to one only, the correspending parts in the two cylinders being given the same reference numerals,`those in the right-hand cylinder being primed.

In the compressor illustrated, 1. designates the compressiony cylinder and 2 the compression tank or reservoir. Mounted within the cylinder is a primary piston 3, affixed .to a 'piston rod 4 and reciprocatedby means ofv the prime mover illustrated generally at 5. Affixed to, and forming part ofthe primary piston 3 is a cylindrical extension 6 defining a recess in which is seated a secondary piston 7 to which is aiiixed a sleeve 8 slidably mounted upon the piston rod 4. Interposed between the base 9 of the recess and the inner face of the secondary piston is a compression coil spring 10 designed normally to hold'the two pistons flush as illustrated in Figure 1, and a .stop 31 is provided for preventing outward movement of the secondary piston beyond the primary. The piston rod 4 is securedto the primary piston through the base 9 which element also forms thebase of the corresponding piston 3 operating in the righthandend of the cylinder, 'and acts as a i Application led August 23, 1927. Serial No. 214,801.

cross head forthe two. A In order to prevent compression of air within the cylindrical eX- tension 6 due to movement of the secondary piston therein, communication with the atmosphere is effected through av bore 11 in the 55 piston rod 4. Y

Atmospheric air enters the cylinder through a port 12 controlled by means of a poppet valve 13 positively actuated by a pivoted arm 14 connected to a link 15 reciprocat- G0 ed in proper timed relation by means of the prime mover. The cylinder communicates with the tank 2 by means of'ducts 16 and 17 enteringthrough the cylinder head and a duct 18 entering through the side wall ofthe cylinder. Duct 16 is provided with a poppet valve 19 positively actuated by means of' a cam 2O on a rotary shaft 21 while communication between the cylinder and the duct 18 is controlled by means of poppet valve 22, positively actuated like valve 13 by lmeans of a pivoted arm 23 connected to a link 24 similarly reciprocated by the prime mover. The duct 17 is provided with-a spring actuated outwardly opening valve 25. The spring is set to permit openingof the valve as soon as the pressure in the cylinder exceeds that in the tank. l 1

Outward movement of the secondary piston, 7 which would normally accompany that of the primary piston 3, is prevented by means of a latch 26 on the sleeve 8 against which abuts a pivoted pawl 27 oscillated at the proper time by a rod 28 operated by means of a cam 29 on the cam shaft 21. v

The cylinder is provided at the end remote from the intake valve 13 with a by-pass 30, the ends of which enter the cylinder at points spaced apart bya distance substantially equal tothe thickness of the primary piston. 90 The function of this by-passwill be made clear in connection with the description of the the general operation. y

I shall now describev the operation of the compressor with particular reference to Figures 2, 3, 4 and 5. Starting with the parts as illustrated in Figure 2, the primary piston 3 is moved to the left. At this time the poppet valves 13 and 19 are opened and poppet valves 22 and 25 closed. The paw127 is n the posilo tion illustrated, abutting against latch 26 so that although the annular primary piston 3 moves forward, the secondary piston remains fixed and consequently compresses the spring 10. The effect of the forward movement of the primary piston is to move the air in the cylinder which is initially at tank pressure, through duct 16 and into the tank. At the same time the corresponding valve 19 at the other end of the double cylinder is opened so that air at tank pressure enters behind the moving piston 3 in that end of the cylinder. rIhe primary pistons are therefore substanl tially balanced considering the pressures on their outer faces. Meanwhile, however, atmospheric fair has been drawn in through port 12 bythe opening of valve 13 and ,now

ffills the annular space behind the primary piston B'while air at tank pressureis being moved into the tank throughduct 18.

When the primary piston 3 reaches the end .Of itsstroke as illustratedin Figure 3 it uncovers the inner port .of bypass 30 Athereby connecting the annular space lilled with atmospheric air with the space on the other Side of the piston which is filled with air at tank pressure. t this point, the valves 13 and 19 are closed, the position Vof the parts being illustrated in Figure 3.

With the closing of the valves 13 and 19, the pawl27 is swung out of engagement with the latch 26, thus freeing the secondary piston and permitting the compressed spring 10 to move the secondary piston outward until flush with the primary piston, the positon of the parts after this movement being illustratedin Figure 4. As soon as the primary piston uncoversv the inner port ofthe by-pass 30, theair at tank pressure passes into the annular space behind the primary piston and mingles with the atmospheric air that has just `been ldrawn in thereby raising its pressure. It is, of course, not raised to tank pressure because the valve 19 has been closed, but

'is raised to some pressurev intermediate atmospheric and tank pressure. At this point, the action of the' secondary piston comes into play and speeds up the movement of the air through the by-pass into the cylinder at the same time slightly raising the pressure in the entire system. In order to prevent :the pres- Sule from rising above thatv of .the tankthe valve 25 is provided, automatically opening to relieve any excess pressure in the cylinder.

'Qn the returnstroke, primary piston '3 and secondary .piston 7 move together. VValve 22 is opened 'so that air in the cylinder is unquestionably at tankV pressure vand the air which has just beendrawn in and raised vto tankpressure is moved through duct 18 Yand into the tank. At the same time, the valve 19 is again opened so that thel pressure on rthe rear'of the moving piston is also at tank pressure. On the return stroke the conditions areV precisely the samey as on 'the outward cylinders. This means thatthe load is substantially uniform throughout the compression stroke and that comparatively little Vheat is generated within the cylindenthe attendant. advantages of this being Well understood by those skilled inthe art. The outward movement of ythe secondary piston does not compress any .air above tank pressure, but does accelerate the movement of the air Vthrough the by-pass and assists in speedily bringing all of the air within'the cylinder up to tank pressure. It has what may .be described as a follow-up action. c

1I have refrained from describing the vprime lmover .as it in itself formsno lpart of this invention. It is also to be understood that the operation of this, prime `mover is automatically controlled by thepressure in the. tank 'l s0 that when the pressure has been brought up to the requiredpressure, say one hundred pounds, `the compressor stops-and when this pressure falls the compressor is automatically f started again. Ifclaimt y '.1. An air compressor comprising thecombinationof -a tank, a compressionylinder, a

piston .in the cylinder, an intake valve, a dis- 1 Y charge valve leading to the tank and means for introducing air at tank pressureinto the cylinder at the termination of the intake stroke. f

-. 2. An air compressor comprising thecombination of a tank, a compression cylinder, a .pistonin the cylinder, an intake valve and a discharge valveleading to the tank at one end oit-the cylinder, a duct leading to the `tank communicating with the other end of the cylinder, andV a ley-pass at the end ofthe cylinder remote fromthe intake and discharge valves whereby air at tank pressure may pass'around Vthe piston at .the end of the intake stroke and mingle Vwith the intaken air.

3.V An air compressor comprisingV the combination of a tank, a compression cylinder, a pistonV in the cylinder, an intake valve, a discharge valve leading to the tank, means for introducing airat tank pressure into the cylinder at the termination of the intake strokefand a duct connecting thev cylinder behind the piston with the tank during thedischargestroke. .1 Y An air .compressorcomprising the comfris bination of a tank, a compression cylinder, a primary piston in the cylinder, a secondary piston carried by the primary piston, an intake valve and a discharge valve leading to the tank at one end of the cylinder, a duct leading to the tank communicating with the other end of the cylinder, a valve in the duct, means for moving the primary piston while the secondary piston remains relatively iiXed, a by-pass at the end of the cylinder remote from the intake and discharge valves whereby air at tank pressure may pass around the piston at the end ofthe intake stroke of the primary piston and mingle with the intaken air, means for closing the valve in the duct at the end of the intake stroke of the primary piston, and means for moving the secondary piston to accelerate the movement of the air through the by-pass.

5. A double acting air compressor comprising the combination of a tank, a pair of cylinders, a piston in each cylinder, means connecting the two pistons so that they move in unison, intake and discharge valves near the inner end of each cylinder, a duct leading from the discharge valves to the tank, a duct near the outer end of each cylinder leading to the tank, a control valve in each said duct, and means for reciprocating the pistons and operating the valves whereby during each stroke atmospheric air is drawn into one cylinder and air at tank pressure moved from that cylinder into the tank while air at tank pressure is forced from the other cylinder into the tank and air at tank pressure permitted to enter behind the moving piston in that cylinder.

6. A double acting air compressor comprising the combination of a tank, a pair of cylinders, a piston in each cylinder, means connecting the two pistons so that they move in unison, intake and discharge valves near the inner end of .each cylinder, a duct leading from the discharge valves to the tank, a duct near the outer end of each cylinder leading to the tank, a control valve in each said duct, a by-pass near the outer end of each cylinder, and means for reciprocating the pistons and operating the valves whereby during each stroke atmospheric air is drawn into one cylinder and air at tank pressure moved from that cylinder into the tank while air at tank pressure is forced from the other cylinder into the tank and air at'tank pressure permitted cylinder, the intake valves communicating with the atmosphere and the discharge valves communicating with the tank, means for reciprocating the pistons, means for opening the intake valve in one cylinder at the beginning of the intake stroke of the piston in that cylinder and means for opening the discharge valve in that cylinder at the end of the intake stroke whereby air at tank pressure is permitted to enter and mingle with the intaken air.

In testimony whereof I aiiix my signature.

LAWRENCE H. HYATT.

to enter behind the moving piston in that cylinder, the by-pass permitting air at tank pressure to pass around the piston in the iirst cylinder at the end of the intake stroke and mingle with the atmospheric air which has been drawn in.

7. A double-acting air compressor comprising the combination of a tank, a pair of cylinders, a piston in each cylinder, means connecting the two pistons so that they move in unison, intake and discharge valves in each 

